The Effect of the Axial Heat Transfer on Space Charge Accumulation Phenomena in HVDC Cables

Giuseppe Rizzo, Pietro Romano, Antonino Imburgia, Fabio Viola and Guido Ala
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Giuseppe Rizzo: L.E.PR.E. HV Laboratory, Dipartimento di Ingegneria–Università di Palermo, Viale delle Scienze, Edificio 9, 90135 Palermo, Italy
Pietro Romano: L.E.PR.E. HV Laboratory, Dipartimento di Ingegneria–Università di Palermo, Viale delle Scienze, Edificio 9, 90135 Palermo, Italy
Antonino Imburgia: L.E.PR.E. HV Laboratory, Dipartimento di Ingegneria–Università di Palermo, Viale delle Scienze, Edificio 9, 90135 Palermo, Italy
Fabio Viola: L.E.PR.E. HV Laboratory, Dipartimento di Ingegneria–Università di Palermo, Viale delle Scienze, Edificio 9, 90135 Palermo, Italy
Guido Ala: L.E.PR.E. HV Laboratory, Dipartimento di Ingegneria–Università di Palermo, Viale delle Scienze, Edificio 9, 90135 Palermo, Italy

Energies, 2020, vol. 13, issue 18, 1-18

Abstract: To date, it has been widespread accepted that the presence of space charge within the dielectric of high voltage direct current (HVDC) cables is one of the most relevant issues that limits the growing diffusion of this technology and its use at higher voltages. One of the reasons that leads to the establishment of space charge within the insulation of cables is the temperature dependence of its conductivity. Many researchers have demonstrated that high temperature drop over the insulation layer can lead to the reversal of the electric field profile. In certain conditions, this can over-stress the insulation during polarity reversal (PR) and transient over voltages (TOV) events accelerating the ageing of the dielectric material. However, the reference standards for the thermal rating of cables are mainly thought for alternating current (AC) cables and do not adequately take into account the effects related to high thermal drops over the insulation. In particular, the difference in temperature between the inner and the outer surfaces of the dielectric can be amplified during load transients or near sections with axially varying external thermal conditions. For the reasons above, this research aims to demonstrate how much the existence of “hot points” in terms of temperature drop can weaken the tightness of an HVDC transmission line. In order to investigate these phenomena, a two-dimensional numerical model has been implemented in time domain. The results obtained for some case studies demonstrate that the maximum electric field within the dielectric of an HVDC cable can be significantly increased in correspondence with variations along the axis of the external heat exchange conditions and/or during load transients. This study can be further developed in order to take into account the combined effect of the described phenomena with other sources of introduction, forming, and accumulation of space charge inside the dielectric layer of HVDC cables.

Keywords: space charge; thermal rating; HVDC cables (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2020
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (2)

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